Cold Deep-Sea Water to Provide Air Conditioning in Downtown Honolulu

A project to replace traditional, energy-intensive air conditioning systems with technology that will use cold, deep-sea water to cool buildings throughout downtown Honolulu, Hawaii, took another step forward recently.

The company undertaking the project, Honolulu Seawater Air Conditioning, has released a preparation notice for its environmental impact statement, which is the first step in a required review process, the Honolulu Advertiser reported recently.

The proposed 25,000-ton seawater air conditioning district cooling system will use a 4-mile, 63-inch diameter intake pipe to collect 45 degree F sea water from a depth of some 1,600 feet under the surface.

The plan calls for cold water to come ashore and be run through a heat exchanger to chill fresh water circulating in a closed loop pipe system. The sea water will be returned to the ocean at between 80 and 200 feet deep and at some 56 degrees F. The fresh water will then be piped to buildings in downtown Honolulu to provide cooling.

The company estimates that most buildings are likely to see an approximate 8% decrease in their air conditioning costs in the first year, with increased savings as the price of oil rises.

The project is estimated to cost some $145 million. The company hopes to have the system operational by late 2009.